CMOS Image Sensor Circuit Layout for X-ray Imaging
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Solution Overview
Problem
CMOS image sensors used in X-ray imaging suffer from layout asymmetry in column read-out circuitry, leading to visible image effects and increased susceptibility to electromagnetic interference, which complicates noise correction.
Innovation Solution
Positioning a part of the circuit elements outside the active region and another part within the matrix of active pixels, with vertical drivers distributed over multiple columns in a central part of the active region, minimizes asymmetry and maintains sensitivity, allowing for correction using Flat Field Correction software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If all column read-out circuitry is positioned below the middle section of the active region in chamfered parts, then space is released below the active region to position vertical driver circuitry, but layout asymmetry occurs leading to visible image effects and increased susceptibility to electromagnetic interference
Solution Approach 1:
The column read-out circuitry is divided into two separate parts: one part positioned outside the active region along one of the first sides, and another part positioned within the matrix of active pixels remote from the second sides. This segmentation allows each part to be optimally positioned, reducing layout asymmetry and improving image quality while maintaining space efficiency.
2Ease of manufacture
If column read-out circuitry is positioned in chamfered parts below the active region, then vertical driver circuitry can be positioned below the active region, but relative long wires connected with column read-out lines become more prone to electromagnetic interference
Solution Approach 1:
Instead of positioning all column read-out circuitry in a single location below the active region, the circuitry is distributed across different spatial dimensions: part outside the active region along the first sides and part within the matrix remote from the second sides. This dimensional distribution reduces wire length and minimizes exposure to electromagnetic interference.
3Area of stationary object
If circuit elements are positioned asymmetrically in chamfered regions, then space utilization is optimized, but asymmetry leads to visible effects in the image that are difficult to correct
Solution Approach 1:
The invention intentionally introduces a controlled asymmetry by positioning part of the column read-out circuitry within the active region matrix remote from the second sides, while keeping part outside along the first sides. This controlled asymmetric positioning balances the overall layout, reducing visible image effects while maintaining efficient space utilization in the chamfered regions.
Data Source
AI summary
The invention relates to a semiconductor device with a semiconductor body comprising a CMOS image sensor with an active region having viewed in projection first sides and second sides perpendicular to the first sides said active region comprising a matrix of active pixels arranged in rows and columns, each pixel having a photosensitive region, the device further comprising a plurality of circuit elements for operating the pixel in the image forming process, the plurality of circuit elements comprising a first set of circuit elements for read-out of the columns and a second set of circuit elements for controlling the rows.According to the invention a first part of the plurality of circuit elements is positioned outside the matrix along one of the first sides and a second part of the plurality of circuit elements is positioned within the matrix of active pixels remote from the second sides. Preferably the first part elements comprises the read-out circuitry of the columns and the second part elements comprises the control circuitry of the rows, the latter preferably being distributed over a number of centrally positioned columns. A device according to the present invention is very suitable for X-ray medical imaging.